Spectroscopic, thermal analysis, and nematicidal evaluation of new mixed ligand complexes of bidentate Schiff base and 1,10 phenanthroline with some transition metals

Abstract

Mononuclear Co(II), Cu(II), Y(III), Zr(IV), La(III), and U(VI) complexes of 2‐[(2‐hydroxybenzylidene)‐amino]‐benzoic acid (H2L) ligand in presence of 1,10‐phenanthroline (Phen) were synthesized and characterized by elemental analysis, spectroscopic techniques (IR, UV–vis, and 1H‐NMR), X‐ray powder diffraction and magnetic measurements. The results prove that H2L acts with the mentioned metal salts as a bidentate ON donor ligand and Phen as an NN donor ligand. The calculated bond length and force constant F(UO) in the uranyl complex are 1.732 Å and 708.90 nM−1, respectively. The electronic spectra and the magnetic susceptibility data support the octahedral geometry for the mononuclear Co(II), Y(III), Zr(IV), La(III), and U(VI) complexes and square‐pyramidal geometry for the Cu(II) complex. Thermogravimetric analysis was performed to determine the thermal stability of the synthesized compounds. The kinetic parameters, that is, the activation energy (E*), pre‐exponential factor (A), entropy of activation (ΔS*), enthalpy of activation (ΔH*) and free energy of activation (ΔG*), of the thermal degradation process were evaluated using Coats–Redfern (C–R) and Horowitz–Metzger (H–M) methods for all the complexes, and the best fit results could be obtained. In the present work, all the synthesized complexes showed nematicidal activity against the root knot nematode (Meloidgyne javanica) by inhibiting egg hatching and causing larval mortality of second‐stage juveniles.

Mononuclear vs. binuclear carboxylates of copper(II) with 2,2′‐bipyridine: Synthesis, characterization, structural description, and properties

“…Absorption spectroscopy yielded broad bands at λ max = 658 and 676 nm (upper most peak in Figures A and A), which are ascribed to transitions of Cu 2+ ion in a six‐coordinated complex as observed in other copper complexes in solution . As complex 2 has square pyramidal geometry in solid state, there might be attachment of a DMSO molecule to a copper ion in solution to form an octahedral coordination around the metal ion.…”

Study on the nematicidal activity and chemical structure of NO bidentate Schiff base some metal complexes

“…The mode of bonding of L with Co(II), Cu(II), Y(III) Zr(IV), La(III), and U(VI) ions was elucidated by comparing the recorded infrared spectra of the complexes with those of the free L. The main IR bands and their assignments are shown in Figure S1 and listed in Table . For L, the absorption bands were observed at 3,436 and 3,270 cm −1 , assigned to the stretching vibrations of ν(OH) for hydroxyl of the phenolic and carboxylic groups . The IR spectra of the complexes exhibited characteristic bands in the region 3,436–3,229 cm −1 , which correspond to ν(OH) indicating that the complexes contain phenolic groups and water molecules in their formula.…”

“…Table collects the absorption spectra of L, ( 1 ), ( 2 ), ( 3 ), ( 4 ), ( 5 ), and ( 6 ). The electronic spectrum of L in DMF (Figure S2) displayed two bands at 273 nm (36,630 cm −1 ) and 336 nm (29,762 cm −1 ), which may be assigned to π–π* and n –π* transitions . The absorption bands (λ max ) for the complexes shifted to higher and lower values attributed to chelation behavior of L toward metal ions .…”

“…The singlet signals at δ: 6.47–6.94 ppm were attributed to –HC=N aliphatic, multiplet at δ: 7.01–8.86 ppm to –CH aromatic, and two singlet signals at δ: 10.26 and 11.22 ppm correspond to –OH of phenol and caboxylate groups (Table ) . Also, the 1 H NMR spectra of complexes exhibit a new signal in the range 3.3–3.85 ppm, due to the presence of water molecules in the complexes …”

“…The Schiff base (L) was synthesized by mixing an ethanolic solution of anthranilic acid 1 mmol (0.137 g) with salicylaldehyde 1 mmol (0.122 mL) into a round bottomed flask equipped with a magnetic stirrer in the presence of 1 mL glacial acetic acid. The reaction mixture was boiled under reflux for 10 hr and then concentrated to 8 mL in a water bath and allowed to cool at 0°C . The formed red precipitate was filtered off, washed several times with ethanol and dried under vacuum over CaCl 2 .…”